This invention relates to motor driven retractable down draft vent systems for use with range and cooktop appliances.
Down draft ventilation systems for cooktops and ranges which locate the vent inlet opening at an elevated level above the cooktop are well known in the art. Such arrangements are particularly advantageously employed with ranges and cooktops which employ gas surface units so as to prevent the air drawn into the vent from interfering with surface unit operation.
An example of a motor driven retractable down draft vent system may be found in U.S. Pat. No. 4,510,260 to Grace. In the drive arrangement therein disclosed for raising and lowering the retractable vent structure, the retractable vent member is positively connected to the motor through a bellcrank arm pivotally connected at one end to the vent member and at the other end to a wheel driven by the motor. By this arrangement the vent member is pushed upward from its lowered position to its raised position as the drive wheel is rotated by the motor through half a turn. It is pulled to its lowered position when the wheel completes its rotation. Switches are located proximate the wheel to deenergize the motor when the vent member reaches the raised and lowered positions.
A major disadvantage of the drive arrangement above described is that although the pivotally mounted coupling structures employ slot and pin pivot structures which presumably allow limited vertical movement or play of the vent member relative to the drive structure, the positive drive of the motor in returning the vent to its retracted position could exert excessive force on an object obstructing the return of the vent member to its retracted position, resulting in potential damage to the object, the vent member and/or the motor.
It is therefore an object of the present invention to provide a drive mechanism for raising and lowering the vent member which freely disengages from the vent member and continues unhindered to its recessed position in the event an obstacle blocks the return of the vent member to its lowered position.